Hydrogen manufacture using gas turbine driven centrifugal compressors

ABSTRACT

A PROCESS FOR PRODUCING HIGH PRESSURE HYDROGEN WHICH COMPRISES: (A) REACTING A HYDROCARBON WITH STEAM IN A STEAM REFORMER TO PRODUCE H2 AND CO2, (B) CENTRIFUGALLY COMPRESSING AT LEAST A PORTION OF THE H2 AND CO2 IN A CENTRIFUGAL COMPRESSOR, PRIOR TO SEPARATING THE CO2 FROM THE H2, (C) DRIVING THE CENTRIFUGAL COMPRESSOR BY MEANS OF A GAS TURBINE DRIVER, (D) USING AIR WHICH HAS BEEN INCOMPLETELY COMBUSTED AS MOTIVE POWER FOR THE GAS TURBINE DRIVER, AND (E) SUPPLYING HEAT FOR THE ENDOTHERMIC REACTION OF THE HYDROCARBON WITH STEAM IN THE STEAM REFORMER BY BURNING FUEL WITH INCOMPLETELY COMBUSTED EXHAUST AIR FROM THE GAS TURBINE DRIVER.

April 27, 1971 c. s. SMITH ETAL HYDROGEN MANUFACTURE USING GAS TURBINEDRIVEN CENTRIFUGAL COMPRESSORS Filed Aprll 1, 1969 o Hm. s STL Y R c E0w. N T N R 53 0 VWM T E mowmwmmzou N u fl m E am CW uzoN Y 2953200 B w2 mum/G For $26 $213 3 1 88 For 3 mwazxw mzBE; v wT w mwzmommm 232mm25km NI OU M 0, G2 2 C 20655200 A Kim 00 zomm uoma x mowmwmazou mmk Omwmmm zom United States Patent Ofice 3,576,603 Patented Apr. 27, 1971 US.Cl. 23-212 4 Claims ABSTRACT OF THE DISCLOSURE A process for producinghigh pressure hydrogen which comprises:

(a) Reacting a hydrocarbon with steam in a steam reformer to produce Hand (b) Centrifugally compressing at least a portion of the H and CO ina centrifugal compressor, prior to separating the CO from the H (c)Driving the centrifugal compressor by means of a gas turbine driver,

((1) Using air which has been incompletely combusted as motive power forthe gas turbine driver, and (e) Supplying heat for the endothermicreaction of the hydrocarbon with steam in the steam reformer by burningfuel with incompletely combusted exhaust air from the gas turbinedriver.

CROSS-REFERENCE TO RELATED APPLICATIONS This application is acontinuation-in-part of Ser. No. 736,520, filed May 17, 1968, which inturn is a continuation-in-part of now abandoned Ser. No. 665,106, filedSept. 1, 1967, both of which applications are hereby incorporated byreference into the present patent application, particularly that portionof Ser. No. 736,520 and Ser. No. 665,106 relating to centrifugalcompression of H -CO gas mixtures followed by removal of the CO at leastin part by physical absorption of the CO BACKGROUND OF THE INVENTION (1)Field of the invention This invention relates to processes for theproduction, compression and purification of gases; and, moreparticularly, it relates to a process for supplying high pressure, highpurity hydrogen gas at elevated pressure. In a still more particularaspect, the invention relates to a process for obtaining high pressure,high purity hydrogen for use in a hydroconversion process. Byhydroconversion process is meant a process wherein hydrogen is reactedwith hydrocarbons so as to convert the hydrocarbons to more desirablehydrocarbons or hydrocarbon products.

(2) Description of the prior art (A) Means for obtaining raw,hydrogen-rich gas: There are a number of current processes available forthe production of raw hydrogen. Many of these processes use hydrocarbonsas a source of hydrogen. Two of the most widely practiced methods ofobtaining raw, hydrogen-rich gas are steam reforming and partialoxidation.

In typical steam reforming processes, hydrocarbon feed is pretreated toremove sulfur compounds which are poisons to the reforming catalyst. Thedesulfurized feed is mixed with steam and'then is passed through tubescontaining a nickel catalyst. While passing through the catalyst-filledtubes most of the hydrocarbons react with steam to form hydrogen andcarbon oxides. The tubes containing the catalyst are located in areforming furnace, which furnace heats the reactants in the tubes totemperatures of 1,2001,700 F. Pressures maintained in the reformingfurnace tubes range from atmospheric to 450 p.s.i.g. If a secondaryreforming furnace or reactor is employed, pressures used for reformingmay be as high as 450 p.s.i.g. to 700 p.s.i.g. In secondary reformerreactors, part of the hydrocarbons in the efriuent from the primaryreformer is burned with oxygen. Because of the added expense, secondaryreformers are generally not used in hydrogen manufacture but are usedwhere it is desirable to obtain a mixture of H and N as in ammoniamanufacture. The basic reactions in the steam reforming process are:

Because the hydrogen product is used in high-pressure processes, it isadvantageous to operate at high pressure to avoid high compressionrequirements. However, high pressures are adverse to the equilibrium;and higher temperatures must be employed. Consistent with hydrogenpurity requirement of about 95 to 97 volume percent H in the final Hproduct and present metallurgical limitations, generally the singlestage reforming is limited commercially to about 1,550 P. and 300p.s.i.g.

In typical partial oxidation processes, a hydrocarbon is reacted withoxygen to yield hydrogen and CO. Insutficient oxygen for completecombustion is used. The reaction may be carried out with gaseoushydrocarbons or liquid or solid hydrocarbons. Partial oxidation may beaccomplished using air to partially oxidize hydrocarbons and preheatedair, at a temperature of 800 -F. or higher, is advantageous ifavailable. However, for manufacture of high purity hydrogen it isgenerally preferable to use essentially pure oxygen rather than air, asthe use of air necessitates the removal of nitrogen from the partialoxidation effluent.

(B) CO or CO +H S removal: Because most hydrogen-using processes,particularly hydroconversion processes, operate more efficiently withhigh purity hydrogen, it is generally required to remove impurities,such as CO from the raw hydrogen generated in the hydrogen plant beforethe hydrogen is passed to the hydrogen-using process. Perhaps the mostwidespread method of removing CO from other gases is the absorption ofCO in an alkanolamine, such as diethanolamine (DEA) or monoethanolamine(MEA). Largely because of its relatively low molecular weight, MBA isgenerally the preferred absorbent of the alkanolamines. The CO forms aloose chemical bond with the amine when it is absorbed.

In using any of the commonly used alkanolamine absorbents, an absorberand stripper are typically arranged in a figure eight processconfiguration. The CO -containing gas is fed into the bottom of theabsorber where CO is absorbed in downward flowing absorbent. Purifiedgas with the CO removed leaves the top of the absorber. Rich absorbentfrom the bottom of the absorber is passed to the top of a strippingcolumn where it is regenerated as it passes from the top to the bottomof the stripping column. The regenerated absorbent passes from thebottom of the stripper to the top of the absorber to complete the figureeight path of the absorbent as it flows down through the absorber trays,or packing material, absorbing CO A large amount of heat is required tostrip the CO from the MEA absorbent which is typically used because ofthe chemical bond that occurs between the CO and the MEA.

For instance, in a large hydrogen plant producing 135x10 standard cubicfeet per day of hydrogen, over 300x B.t.u.s per hour are generallyrequired to reboil the MBA in order to effect the regeneration of theMEA. These 300x10 B.t.u.s per hour are equivalent to over 1,000,000dollars per year in terms of steam (at a value of about 40 cents perthousand pounds) that could be generated.

Over a period of time, a considerable amount of MBA will be lost out thetop of the absorber as large volumes of gas carry entrained MEA out thetop of the absorber in spite of preventive measures. Further MBA is lostdue to pumping losses as large volumes of absorbent are required andtherefore circulated to remove the great quantities of CO that aretypically formed in modern hydrogen production plants. Other common COabsorption systemsfor example, hot carbonateare generally similar to thealkanolamine system in the respects described above with only moderatereduction in regeneration heat requirements.

Since the alkanolamine abs'orbents tend to degrade, a reclaimer iscommonly used to purify the absorbent. The reclaimer is essentially asmall reboiler. It is fed a slipstream of the absorbent from the bottomof the stripper. Only that portion of the slipstream that is vaporizedis returned to the stripper system. Heavy tarry material collects in thebottom of the reclaimer and is periodically withdrawn and passed tosewerage as a spent alkanolamine stream. Common practice is to clean thereclaimer as frequently as once a week. The cleaning procedure typicallyinvolves taking the reclaimer olfstream, draining the spent alkanolamineand heavy tarry material, and steam cleaning the reclaimer.

It is thus apparent that cleaning the reclaimer will result in losses ofabsorbent in addition to those losses caused by entrainment and pumpingleakage. Although the alkanolamine is expensive, this cleaning procedureis necessaary to avoid build-up of corrosive bodies in the CO absorptionsystem. Corrosion, which would be worse without the reclaimer, still isa considerable problem in the alkanolamine CO absorption systems.

(C) Compression of high purity hydrogen: Some of the processes which usehigh purity hydrogen as a reactant are: hydrodesulfurization, operatingat pressures between about 100 and 1,500 p.s.i.g.; hydrotreating,operating at pressures between about 200 and 2,000 p.s.i.g.;hydrocracking, operating at pressures between about 450 and 3,000p.s.i.g.; and thermal hydrodealkylation, operating at pressures betweenabout 450 and 1,000 p.s.i.g. All of these just-mentioned hydroconversionprocesses may operate at even higher pressures (for example, up to10,000 p.s.i.g.) than just given but seldom will operate at pressureslower than the range given. Thus it can be seen that many of theprocesses which use hydrogen require the hydrogen at a high pressure,which in most cases means generated hydrogen gas must be compressedbefore being passed to a hydrogen-using process.

Basically, all compressors may be considered as belonging to one of twocategories; i.e., their principles involve either that of truemechanical compression (positive displacement) or centrifugalcompression: Compressors utilizing true mechanical compression are soconsidered because the act of volumetric reduction is accomplished bymeans of a compressing element. The compression element may be in theform of a piston which in its particular motion entraps and displacesgas within a suitably designed and fully enclosed housing. Motion may bereciprocating during which the element, in the form of a piston, passesback and forth within dimensional limits over the same course within acylinder in a straight-line direction.

Centrifugal compression is accomplished by centrifugal force exerted onan entrapped gas during rotation of an impeller at high speed. Mostcentrifugal compressors depend primarily on centrifugal force and hightangential velocity of the fluid in the periphery of the impeller (orrotors or blades in the instance of some turbocompressors) to producethe desired head or discharge pressure. In this specification, the termscentrifugal compression or compressor are meant to include turbinecompression or turbocompressors, including, for example, axial-flowcompressors. In the broad sense of centrifugal compression used herein,compression is effected, at least to a substantial degree, by conversionof velocity head to pressure head.

The reciprocating compressor is used for hydrogen compression, but ithas some severe disadvantages, particularly for large-size plants:

(1) All parts are subject to unbalanced, reciprocating stresses; andfoundations, frames and other parts must be large. To minimizevibration, speeds are low (400-700 r.p.m.); and capacity is low.Therefore, in large plants, several machines are required. Cost ofinstalling, instrumenting, protecting and piping several machines ishigh. Considerable land is required, and plants are bigger and morecomplex, making them more dilficult to control.

(2) The reciprocating machine is less reliable than centrifugalmachines, and it is common practice to design plants with one or twoexpensive spare machines ready to come on-stream in the event of afailure.

(3) The reciprocating machine produces a pulsating gas supply whichsonically transmits vibration to piping instruments and other plantfacilities. Such vibrations can cause hazardous failures with hydrogenat high pressure.

(4) The low speed of reciprocating compressors tends to limit primemovers to low speed, electric motors or gas engines. While it ispossible to use high speed steam or gas turbines, large reduction gearsmust be used. The pounding of the reciprocating loads has led to poorexperience with these units. Hydrocracking and hydrogen manufacturingprocesses can be designed to produce byproduct steam if it could be usedin steam turbine drivers. However, for the reasons just given, thisbyproduct steam is generally not used to drive the reciprocatingcompressors.

(5 Reciprocating compressors are particularly susceptible to severedamage if liquid is present in the gas being compressed.

By comparison, centrifugal compressors are reliable, rugged, in mostcases relatively simple, have large capacities, are relatively small,have balanced stresses, and generally cause relatively little vibrationor pulsation in the plants. They can be driven by high speed, steamturbines or gas turbines.

However, centrifugal compressors cannot, with any reasonable degree offeasibility, be used as high purity hydrogen compressors.

Compression ratios (ratio of discharge pressure to inlet pressure forone stage of compression) obtainable with a centrifugal compressor are afunction of the molecular weight of the gas to be compressed. With purehydrogen having a molecular weight of 2, compression ratios are limitedto about 1.025. Because of this low compression ratio for hydrogen,centrifugal compressors are not practical to date for compression ofhigh purity hydrogen.

Table I below illustrates the sharp decrease in compression ratio forcentrifugal compression as the molecular weight of the gas beingcompressed decreases. The number of stages used in the compression isthe same for each case in Table I. i

TABLE I Barometer, p.s.i.a 14. 4 14. 4 14. 4 Inlet temperature,F 60. 060. 0 110. O k (op/0V. for inlet gas) 1. 11 1. 398 1. 36 Inlet capacity,e.f.m 20, 000. 0 20, 000. 0 20, 000. 0 Head, it.-lb. per 1b.. 22, 000. 022, 000. 0 22, 000. 0 Molecular Weight 63. 0 28. 05 10.0 Inlet pressure,p.s.i.a. 16. 73 14. 73 14.08 Discharge pressure, p.s.i.a 79. 53 29. 7317. 99 Compression ratio 4. 75 2. 01 1. 28

As previously indicated, it is not practical to usecentrifugalcompressors to compress high purity hydrogen to highpressures because of the multitude of stages that Would be required. Forexample, the centrifugal compression ratio (ratio of discharge pressureto inlet pressure for one stage of centrifugal compression) withhydrogen, molecular weight of 2, is limited to about 1.025.Consequently, over 75 stages of centrifugal compression would benecessary to bring the pressure of hydrogen up to 1,700 p.s.i.g.starting from a pressure of 200 p.s.i.g. On the other hand, two stagesof a reciprocating positive displacement compressor could increase thepressure from 200 p.s.i.g. to 1,700 p.s.i.g. Thus, in spite of theirproblems previously discussed, reciprocating compressors have heretoforebeen used in bringing high purity hydrogen to high pressure.

British Pat. No. 1,064,182 relates to the production of highlycompressed synthesis gas, which is produced by compression of a gasstream in a synthesis gas compressor driven by a gas turbine. Accordingto the process disclosed in British Pat. No. 1,064,182 a firsthydrocarbon fuel is burned in a compressed stream of air, the air beingin excess of the stoichiometric requirements for the combustion of thehydrocarbon fuel, and then the hot gas stream resulting from suchcombustion is expanded through a gas turbine. A second hydrocarbon fuelis burned with the gases exhausting from the gas turbine, so as tosupply heat for a steam-hydrocarbon reforming reaction. In the reformingreaction a raw synthesis gas stream such as hydrogen methane, and carbonoxides is generated. Nitrogen may be introduced in the synthesis gasstream by burning air with the synthesis gas stream in a secondaryreformer, according to the process disclosed in British Pat. No.1,064,182. A synthesis gas compressor of an undisclosed type is used toelevate the synthesis gas to a high pressure. The synthesis gas might beused, for example, in ammonium synthesis or in methanol synthesis. Ineither case the average molecular weight of the synthesis gas would beconsiderably greater than if only a high purity hydrogen gas stream wasdesired. Although the type of compressor used according to the processof British Pat. No. 1,064,182 is not disclosed, a turbine or centrifugalcompressor may be feasible due to the nitrogen or carbon monoxidepresent in the synthesis gas. Either the nitrogen or carbon monoxidewould, of course, act to considerably raise the average molecular weightof the hydrogen gas stream, thus making the average density of thestream to be compressed greater than if it were a pure hydrogen gasstream.

British Pat. No. 1,064,182 discloses the removal of CO prior tocompressing the synthesis gases. Thus, for the reason given above, theprocess of British Pat. No. 1,064,182 would not be feasible to bringhydrogen up to high pressures because an unreasonable number ofcentrifugal compression stages would be needed.

SUMMARY OF THE INVENTION According to the present invention, a processis provided for producing high pressure hydrogen, which processcomprises:

(a) Reacting a hydrocarbon with steam in a steam reformer to produce Hand CO (b) Centrifugally compressing at least a portion of the H and COin a centrifugal compressor, prior to separating the CO from the HDriving the centrifugal compressor by means of a gas turbine driver,

(d) Using air which has been incompletely combusted as motive power forthe gas turbine driver, and

(e) Supplying heat for the endothermic reaction of the hydrocarbon withsteam in the steam reformer by burning fuel with incompletely combustedexhaust air from the gas turbine driver.

Preferably the gas mixture comprised of H and CO which is centrifugallycompressed contains sufficient C0 so that the molecular weight of saidgas mixture is at least four. In some instances in the process of thepresent invention it is desirable to remove a portion of the CO presentin the hydrogen gas stream generated by steam reforming. However, it isusually preferable that none of the CO present in the H and CO gasgenerated by steam reforming is removed from the H and CO prior tocentrifugal compression of the H and CO Of course, a small amount of COmay be lost from the hydrogen gas which is generated by steam reformingdue to leaks or other merely incidental losses of CO Preferably thecentrifugal compressor compresses the H and CO from a pressure belowabout 450 p.s.i.g. to a pressure of at least about 900 p.s.i.g. toobtain high pressure H and CO In accordance with a preferred embodimentof the present invention, the CO is removed from the high pressure H andCO by absorption of the CO at a pressure of at least 900 p.s.i.g. in aphysical absorbent. A number of advantages are obtained by usingcentrifugal compression instead of reciprocating compressors as is donein accordance with the prior art for high pressure, high purity hydrogenproduction. As explained in our earlier application Ser. No. 736,520,the centrifugal compressor affords a number of operating advantages andin particular is advantageous because of its reliability. Alsosurprising overall economic advantages are obtained by removing the COfrom the hydrogen gas at high pressure obtained by the centrifugalcompression rather than removing the CO from the hydrogen at relativelylow pressures prevailing prior to compression.

It is particularly advantageous to remove CO from the high pressurehydrogen-CO gas mixture by physical absorption of the C0 The physicalabsorbent may be readily and economically regenerated by reducing thepressure on the absorbent. Previously used low pressure absorbents,particularly those absorbents that formed loose chemical 'bonds With COrequired relatively expensive regeneration procedures requiring the useof a substantial amount of steam or other heating medium for theabsorbent stripper.

BRIEF DESCRIPTION OF THE DRAWING The drawing is a schematic flow sheetof a preferred embodiment of the invented process. The schematic flowdiagram illustrates the important step of CO removal subsequent tocentrifugal compression.

DETAILED DESCRIPTION Referring now in more detail to the embodiment ofthe invention shown in the drawing, a hydrocarbon feed stream in line 1is combined with steam in line 2 and introduced to reforming furnace 5for reaction to produce a raw hydrogen gas. Typically the hydrocarbonfeedstock is a light hydrocarbon such as natural gas comprised mostly ofmethane. The hydrocarbon stream is desulfurized using activated carbonor molecular sieves to adsorb sulfur compounds. If excessive sulfurcompounds remain in the feed, the nickel catalyst which is typicallyused to speed up the kinetics of the reaction of methane with H O ispoisoned.

Generally the endothermic reforming reaction in reformer furnace 5 takesplace at a pressure of about 300 p.s.i.g. anda temperature of about1500" F. Thus there is substantial heat present in the hydrogen-rich gascontaining CO and CO withdrawn from the reforming furnace via line 7.This heat is typically removed by heat exchange with boiler feed waterso as to generate steam and cool the reformer efiluent to a temperatureof about 700 F.

The reformer effluent stream at a temperature of about 700 F. is thenpassed via line 7 to CO shift conversion 8 wherein carbon monoxide isreacted with steam to produce hydrogen and CO Preferably shiftconversion zone 8 is comprised of a high temperature shift conversionstep operating at about 650-800 F. followed by a low temperature shiftconversion step operated at about 350- 500 F. The high temperature shiftconversion step employs an iron-chrome catalyst, and the low temperatureshift conversion stage employs a copper-zinc oxide catalyst.

The hydrogen gas steam, now enriched in hydrogen be cause of the COshift conversion, is withdrawn from shift conversion zone 8 via line 9at a temperature of about 350500 F. Heat is then removed from thehydrogenrich gas stream by heat exchange first with boiler feed waterand then with process cooling Water. The hydrogen gas is passed througha separator wherein liquid condensate which is formed by the cooling isseparated from the hydrogen gas. Then the hydrogen gas, which has beensubstantially freed of water but which still contains the CO resultingfrom reforming in steam reformer 5 and shift conversion in zone 8, isintroduced via line 9 to centrifugal compressor 10.

As indicated previously the advantages and many of the other factorspertinent to centrifugal compression prior to complete CO removal aredisclosed in our application Ser. No. 736,520 which application isincorporated by reference into the present application. Because of theCO present in the hydrogen gas feed to centrifugal compres sor 10 themolecular weight of the hydrogen gas is sufiicient so that centrifugalcompression is feasible to obtain high pressure hydrogen, for example900 p.s.i.g. and above. As explained in our earlier application Ser. No.736,520, if essentially all of the CO is removed prior to compressionthen the molecular weight of the gas is too low to make the use ofcentrifugal compressors feasible. Thus reciprocating compressors wouldbe required. Reciprocating compressors, in turn, are not as dependableand in many respects are more expensive than centrifugal compressors.More importantly for purposes of the present invention reciprocatingcompressors are not amenable to drive by means of a gas turbine driver.

Gas turbine 20 drives centrifugal compressor 10 and air compressor 13 bypower transmitted via mechanical linkages 12 and 12a. Gas turbine 20 is,in turn, driven by expanding hot gases which are introduced via line 14and exhausted from the gas turbine via line 4. The hot gases which areused to drive gas turbine 20 are obtained by partially burning air withfuel in firebox 15. Because the combustion (i.e., consumption of theoxygen content) of the air introduced into firebox 15 via air compressor13 and line 16, is incomplete, there is a substantial residual amount ofoxygen remaining in the resultant hot gases introduced to gas turbinevia line 14. Thus, in turn, the expanded exhaust gases from gas turbine20 contain a substantial amount of oxygen as, for example, 50 to 75% ormore of the oxygen in the original air introduced via line 16 to firebox15. The hot gases from the firebox typically enter gas turbine 13 at atemperature of about 1300 to 1700 F. and exhaust at a temperature ofabout 800l000 F. Seldom do the gases exhaust from gas turbine 13 at atemperature less than about 600 F. Thus there is available from gasturbine 20 an oxygen-containing gas which is preheated and thereforeforms an advantageous source of oxidizing gas for burning fuelintroduced via line 3 to steam reformer 5.

Integration of the gas turbine and the centrifugal compressors into theprocess as described above is particularly advantageous because the workenergy required to drive compressor 10 is obtained incrementally at high(in the order of 70%) eificiency.

Typically compressor 10 raises the pressure of the hydr0gen-CO mixturefrom about 200 p.s.i.g. to a pressure between about 1500 and 3500p.s.i.g. Thus, a mixture of high pressure hydrogen and CO is removedfrom the centrifugal compressor via line 11. CO is removed from the CO-hydrogen gas mixture at high pressure in CO removal zone 18. Preferablythe CO is removed by absorption of CO into a physical absorbent. Byphysical absorbent is meant an absorbent which may be freed of at leasta majority (more than 50% of the CO which would be absorbed in theabsorption step, by means of reducing the pressure from the absorptionpressure down to a substantially lower pressure as, for example, down toa pressure between about atmospheric pressure and p.s.i.g. As discussedin our Ser. No. 736,520 it is surprisingly advantageous to utilize highpressure CO removal, particularly using a physical absorbent inconjunction with centrifugal compression of the hydrogen-CO gas mixture.

Product hydrogen is withdrawn from (lO -removal zone 18 via line 19. Theproduct hydrogen may be used directly in a hydroconversion unit such asa hydrocracker or a hydrotreater. However, in a typicalhydrogen-manufacturing train, hydrogen gases obtained from the CO-removal zone will be subjected to a methanation step in order toconvert some residual amounts of carbon oxides to methane, because thecarbon oxides are usually detrimental to the hydrogen conversionprocess.

Although the process of the present invention is directed to a steamreforming hydrogen manufacturing process, the basic concept of thepresent invention may also be applied to partial oxidation hydrogenmanufacturing process. As discussed previously, preheated air is notgenerally used in partial oxidation hydrogen production because aircontains nitrogen which must be removed from the hydrogen. However hotexhaust air (from a turbine used to drive the hydrogen centrifugalcompressor) is advantageously used (i.e., burned with fuel to supplyheat) in furnaces to preheat hydrocarbon (e.g., oil or natural gas) and/or oxygen and/ or water fed to the partial oxidation reactor.

Although various specific embodiments of the invention have beendescribed and shown, it is to be understood that they are meant to beillustrative only and not limiting. Certain features may change Withoutdeparting from the spirit or essence of the invention. It is apparentthat the present invention has broad application to the production ofhigh pressure hydrogen using a centrifugal compressor which is driven bya gas turbine. Accordingly, the invention is not to be construed aslimited to the specific embodiments illustrated but only as defined inthe appended claims.

We claim:

1. A process for producing high pressure hydrogen which comprises:

(a) reacting a hydrocarbon with steam in a steam reformer at a pressurebelow about 450 p.s.i.g. to obtain a hydrogen-rich gas containingsufficient CO so that the molecular weight of the hydrogen-rich gas isat least 4;

(b) compressing the hydrogen from a pressure below 450 p.s.i.g. in acentrifugal compressor to a pressure of at least 900 p.s.i.g., beforethe molecular weight of the hydrogen-rich gas is reduced below 4 by C0removal, to obtain high pressure hydrogen-rich gas;

(c) removing CO from the high pressure hydrogenrich gas to obtain highpurity high pressure hydrogen, at least part of the CO being removed byabsorbing CO in a physical absorbent;

(d) driving the centrifugal compressor by means of a gas turbine usingair which has been incompletely combusted as motive power for the gasturbine, and

(e) supplying heat for the endothermic reaction of the hydrocarbon withsteam in the steam reformer by burning fuel with incompletely combustedexhaust air from the gas turbine.

2. A process in accordance with claim 1 wherein the hydrogen-rich gasobtained from the steam reformer is fed to a CO shift conversion zonewherein CO present in the hydrogen-rich gas from the reformer is reactedwith H O to produce additional H and CO prior to compression of the H inaccordance with step (b).

3. A process in accordance with claim 1 wherein the hydrogen iscentrifugally compressed after partial removal of CO from thehydrogen-rich gas generated by steam reforming.

References Cited UNITED STATES PATENTS 5/1968 Habermehl et a1 232135/1968 Carson 55-44 10 3,401,111 9/1968 Jackson 208108 3,418,082 12/1968Ter Haar 23-213 3,420,633 1/1969 Lee 23-210 FOREIGN PATENTS 1,064,1824/1967 Great Britain 23-212 EDWARD STERN, Primary Examiner

